A couple of quick thoughts (transcript here):
1.) I'd say this isn't so much a new speech as a reversion to McCain's convention speech, albeit in shorter form. Structurally, they're very similar. The opening half is a series of small-bore comparisons with Obama--he'll raise your taxes and kill jobs, I'll cut taxes and create jobs; he'll force you into government-run health care, I'll give you choices and competition; etc. The second half of the speech is more lyrical, with the classic McCain-Salter themes of duty, honor, and sacrifice on prominent display. In fact, the closing flourish borrows directly from the convention speech at times.
My guess is that the McCaniancs were never riding so high as right after the convention and wanted to recapture some of the old magic. Problem is, those were the days before Sarah Palin became a punchline, before the financial markets went into freefall, and before McCain's erratic behavior became a central campaign meme. I'm not sure this speech does much to address those issues.
On top of which, the portion of the speech probably most responsible for McCain's convention bounce--the vivid and moving recounting of his POW experience--is absent here. (And, in any case, it wouldn't pack the same punch the second or third time around. Much its power came from its novelty.)
2.) There are really just two new twists here. One is a nearly-explicit rebuke to George W. Bush. The other is McCain's attempt to cast himself as a check on Democratic control. I don't think the first twist is credible. "We cannot spend the next four years as we have spent much of the last eight: waiting for our luck to change," McCain says. "The hour is late; our troubles are getting worse; our enemies watch." It's a noble sentiment. But, if that's really how McCain felt all this time, why wait till the last three weeks of the campaign, when his poll numbers were collapsing, to unburden himself? I think the desperation is too transparent.
The check on Democratic rule is more promising. Americans do have a deeply-ingrained aversion to unchecked power. But I wonder if it resonates as much during an economic crisis, when voters crave action not checks and balances. McCain's whole problem is that Democratic rule is precisely what voters seem to want when their jobs and savings are at stake.
For this to work, McCain is going to have to paint a picture of Democratic governance that's much scarier than the one he's painting--and much scarier than the status quo. I'm not sure that's possible.
Finally, running against unified Democratic control implicitly cuts loose his GOP colleagues in Congress. While it's hard to see how Republicans take back either chamber, I'm not sure they want to be written off just yet, which could only aggravate their losses. It's not hard to imagine this creating internecine problems.
3.) McCain still faces the same basic dilemma he faced heading into last week's debate: On the one hand, he needs to do something dramatic to catch up. On the other hand, doing something dramatic would reinforce his reputation for unsteadiness, which is a big part of his problem. McCain needs to come off as more even-keel, not less.
This speech tries to square that circle--appearing to be new and dramatic without offering much that could be described that way--and ends up accomplishing neither goal. It could help him marginally, but I don't see it altering the race.